Polymers of acrylic acid alkyl esters are known as acrylic rubbers. These acrylic rubbers are excellent in heat resistance and further in resistance against lubricant oil, and thus are widely used as an oil seal and so on. The acrylic rubbers, however, have no resistance against fuel oils having a lower aniline point than lubricating oils, such as gasoline, and thus they are applicable only to lubricating oils.
In order to improve the fuel resistance of acrylic rubbers, an attempt to use as a copolymerization component monomers having a functional group of high polarity, such as a cyano group and a fluorine-containing group, has been made. However, the introduction of such polar groups increases the glass transition point of the resulting copolymer and can provide only copolymer elastomers having poor low-temperature characteristics.